In the related art, an oxygenator which performs gas exchange using a hollow fiber membrane layer constituted with a plurality of hollow fiber membranes is known (for example, see Japanese Patent No. 4041254).
The oxygenator described in Japanese Patent No. 4041254 has a housing, hollow fiber membrane layers which are housed in the housing and form a cylindrical shape as a whole, a blood inlet, a blood outlet, a gas inlet, and a gas outlet. In the oxygenator, through each hollow fiber membrane, gas exchange between blood and gas, that is, a process of adding oxygen and removing carbon dioxide occurs.
In the hollow fiber membrane layers having a shape of a cylindrical body, a plurality of hollow fiber membranes are integrated and laminated on one another. In each of the layers, hollow fiber membranes are wound one by one around the central axis of the cylindrical body, and in this state, the hollow fiber membranes travel between a partition at one end of the cylindrical body and a partition at the other end of the cylindrical body.
In an outward path heading toward the partition at the other end from the partition at one end, each hollow fiber membrane is wound at least once around the central axis of the cylindrical body. Moreover, in a homeward path heading toward the partition at one end from the partition at the other end, each hollow fiber membrane is also wound at least once around the central axis of the cylindrical body.
Each of the hollow fiber membranes wound as above has a problem in that the larger the number of times the membrane is wound, the greater the total length of the hollow fiber membranes become, and a degree of pressure loss of the gas passing through the inside of the hollow fiber membrane increases in proportion to the total length.
In this case, gas exchange performed through each hollow fiber membrane may not easily occur.